//x的算数平方根
public class leetcode69 {
    public int mySqrt(int x) {
        //return (int)Math.sqrt(x);
        if(x<1) return 0;
        long left=1;
        long right=x;
        while(left<right){
            long mid=left+(right-left+1)/2;
            if(mid*mid<=x){
                left=mid;
            }else{
                right=mid-1;
            }
        }
        return (int)left;
    }
}
